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What is called matter and what is called antimatter is just a convention, isn't it? For example, suppose we call the bottom, the charm and the down quark antimatter and we call the strange, top, and up quark matter. So then one can say that for some particles there was a little bit more matter in the early universe, while for other particles there was a bit more antimatter. This sounds less strange than saying that there was more matter for all particles. What is wrong with this idea?

Qmechanic
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anoniem
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    Sure but that is somewhat arbitrary. You can go particle per particle basis. For example, tou can just forget everything and then ask why is there more electrons than positrons, this the lightest stable lepton, there should not be an asymmetry... but there is one anyway. – Mauricio Mar 05 '24 at 18:23
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    Then we'd need another name for what electrons and positrons are with respect to one another....and this new term would be the same asymmetry as before. – Triatticus Mar 05 '24 at 18:25
  • I see, it does not solve the asymmetry. But per particle looks a bit more manageable :) – anoniem Mar 05 '24 at 18:33
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    Is it clear to you that the down quark is not antimatter in the ordinary system? Up and down are both matter, and anti-up and anti-down are antimatter. In your system "matter" and "antimatter" aren't even antiparticles. Yes, we could call the anti-up "matter" and the up "antimatter", in that sense matter vs antimatter is arbitrary, but not the in way you propose. The question is why there are more of some particles than their antiparticles. Redefining antimatter to a useless definition doesn't solve this, it just makes it a lot more confusing why you try to discuss the problem. – AXensen Mar 05 '24 at 18:51
  • @AXensen: I don't have a system. But you always hear "there is much more matter" and you tend to think that "matter" is some special property of all particles. But it is just a name convention. – anoniem Mar 05 '24 at 19:11
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    It is not a name convention, The names apply to matter and antimatter in order to classify observations that finally led to the standard model of particle physics. read carefully https://en.wikipedia.org/wiki/Antimatter – anna v Mar 05 '24 at 19:37
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    Sorry I think I've just understood... did you mean you want up and anti-down to be called "matter," and down and anti-up to be called "antimatter?" If so, you should consider that the actual problem in cosmology is the "baryon asymmetry" not just "matter vs antimater" https://en.wikipedia.org/wiki/Baryon_asymmetry. The standard model tells us that "baryon number" is conserved, not an arbitrarily defined "matter vs antimatter." So in that sense, if up is matter, then down is also matter. People might reopen if you clarified what your current knowledge is and what you meant by the question. – AXensen Mar 05 '24 at 22:02
  • I put the quarks in alphabetical order. But looking at the wikipedia Quark article, it may seem more logical to call the up, charm, and top quark to be antimatter, and the down, strange, and bottom quarks matter (or vice versa). But maybe then the definition of the total baryon number of a system has to be changed as well. But this probably won't work. Thanks to all for your answers! – anoniem Mar 07 '24 at 08:28

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